The Regina is a Swedish model of electric multiple unitpassenger train, manufactured by Bombardier Transportation (formerly ADtranz). It is used by the national passenger railway SJ along with numerous regional and private operators, in variants designated X50, X51, X52, X53, X54 and X55, and in two-, three-, and fourcarriage models. The Regina is wider than other Swedish trains; at 3 450 mm, it allows five-across seating, increasing passenger capacity by 25%. The car body is built of stainless steel, with only bolsters and coupler pockets made of mild steel. The length is 54, 80 and 105 m, and the capacity 165-294 seats. A variant of the Regina is used in China as the CRH1.

Top speeds of various models range from 180 km/h to 200 km/h (112 mph to 125 mph). As part of the Gröna tåget (‘the green train’) project, a modified Regina set the Swedish rail-speed record of 303 km/h (188 mph) on 14 September 2008;[2] the goal is to reach 250 km/h (155 mph) in regular service.[3]

The existing Regina units are short trains built for local and regional service, but in late 2007 it was announced that SJ were ordering twenty units furnished for inter-city service.[4] These trains, designated X55, were delivered during 2011 and 2012, and are used on the routes connecting Stockholm with destinations like Sundsvall, Värmland and Dalarna, allowing the displaced X 2000 units to be used instead to lengthen the busy trains running to Göteborg and Malmö.[5] These units are four-carriage trains with a first-class section and an on-board bistro; four-across seating. There is an option for another 20 units.[1]